An oven can be one of the most difficult kitchen appliances to clean. Food that splatters onto the interior surfaces of the oven during cooking usually becomes baked-on, making the removal thereof particularly difficult. If interior surfaces of the oven are not regularly cleaned, the amount of baked-on food can build up rapidly, thereby making subsequent cleanings more difficult.
There are several known methods for facilitating the removal of baked-on food and soils from the interior surfaces of ovens. The most widely used cleaning methods involve pyrolysis of the baked-on soils (pyrolytic cleaning), the application heated water or steam to the baked-on soils (aqualytic cleaning or aqualysis), or the application of highly alkaline chemical oven cleaners to the baked-on soil (chemical cleaning). Although these known methods are relatively effective for removing baked-on food from the interior surfaces of ovens, they present several disadvantages.
Pyrolytic cleaning of ovens typically involves heating the interior of the oven to temperatures of about 480-500° C., or about 900-930° F., for several hours. Many ovens feature a high-temperature self-cleaning cycle, during which baked-on foods are pyrolyzed (i.e. decomposed) to carbon ash residue that can be wiped from the interior surfaces of the oven once it cools. To be effective, such pyrolytic heating cycles must maintain the temperature within the oven cavity above about 480° C. (900° F.) for a period of approximately 60-180 minutes (1 to 3 hours), during which time the ovens are often automatically locked and cannot be opened.
A number of disadvantages associated with pyrolytic cleaning include the amount of time required for proceeding through a pyrolytic cleaning cycle, which can extend up to about three hours. There is also a tendency for the porcelain enamels applied to the interior surfaces of ovens to craze, and in some cases flake off when they are repeatedly exposed to such elevated temperatures. Moreover, ovens having pyrolytic heating cycles are more expensive to manufacture than conventional ovens due to the need for extra insulation and automatic door locking features. Furthermore, such ovens are more expensive to operate than conventional ovens because much power is used to generate and maintain the high temperatures during the pyrolytic heating cycle. Such ovens can also present safety concerns because the exterior surfaces of the oven can become quite hot during the pyrolytic heating cycle.
One lower-temperature pyrolytic method for removing baked-on soil from the interior surfaces of ovens is referred to as catalytic cleaning, and involves the use of catalytic enamel compositions formed on the interior surfaces of ovens. Catalytic enamel compositions, such as the composition disclosed in Faust, U.S. Pat. No. 4,084,975, typically have a porous surface and contain a substantial quantity of metallic oxides that can catalyze the oxidation of food material that is spilled or spattered on the surface of the enamel. In operation, food material is absorbed into the porous enamel surface where the catalytic metallic oxides catalyze oxidation of the food material at a substantially lower temperature (e.g. around normal cooking temperatures of 300-400° F.) than is required for pyrolytic enamels.
One disadvantage of using catalytic enamels on the interior surfaces of ovens is that the pores in the enamel can rapidly become clogged and saturated with food material, which significantly diminishes the ease with which the enamel can be cleaned. Furthermore, because the surface of a catalytic enamel coating is porous, it is readily subject to staining.
Chemical cleaning methods involving the use of oven cleaners also presents several disadvantages. Specifically, these types of cleaners include significant quantities of caustics, such as sodium hydroxide and/or potassium hydroxide. While such products are relatively effective in their ability to remove baked-on food from the interior surfaces of ovens, they are highly alkaline (i.e. having pH typically greater than about 12) and therefore present safety hazards. Fumes from such cleaner products, which are best used when the oven is warm, can irritate the eyes and throat and can also cause chemical skin burns. Moreover, the resulting product of the chemical reaction between these cleaners and baked-on food is unpleasant to handle.
Aqualytic cleaning methods, also known as steam cleaning or aqualysis, use water or steam to remove baked-on soils. In these methods, heated water (often in the form of steam) is brought into contact with the baked-on soils. Contacting the heated water to the soils for a certain amount of time facilitates separation of the soils from the interior enamel surfaces of the oven. Typically, a pool of water is placed in the oven and heated so that the water turns to steam and the steam contacts the baked-on soils.
Aqualytic cleaning presents several disadvantages. Specifically, the bottom interior surface of the oven may be completely submerged in the water during aqualytic cleaning, while the side and top interior surfaces are only contacted with steam. While this may be advantageous in removing baked-on soil from the bottom surface, baked-on soils on the side and top interior surfaces of the oven may not be fully removed from the enamel during such cleaning. In this respect, aqualytic cleaning may not satisfactorily clean the side and top interior surfaces of the oven. Furthermore, some soils, like grease, have shown particular resistance to aqualytic cleaning, even when submerged in heated water.
Additionally, for aqualytic cleaning to be effective, the enamel coating has to be specifically formulated to optimally release the baked-on food when contacted with water. Such enamel coatings will be referred to herein as “aquarelease” coatings, which are enamel coatings that satisfactorily release baked-on food when subject to water or steam. Even though aquarelease coatings may be specifically formulated to optimally release baked-on food when contacted with water, baked-on soils such as grease may still not be satisfactorily removed during aqualysis because these substances repel the water that is being used for cleaning. This may be especially true on the interior side and top oven surfaces, which are only contacted by water vapor, rather than liquid water. In this regard, it may be advantageous to subsequently use another cleaning method, e.g. pyrolytic cleaning, to completely remove water-repellant baked-on food such as grease, which may be left over after aqualytic cleaning. However, conventional aquarelease coatings are not designed to be subject to pyrolytic cleaning temperatures. If subject to temperatures of about 900° F., the conventional aquarelease coatings undesirably and substantially discolor and exhibit a loss of gloss, which is not acceptable to many oven owners.
As such, there exists a need for a composition that can be applied to the interior surfaces of oven cavities and other articles from which baked-on foods can be easily removed.